294 Professor Marcet on the 



have become nearly insensible to this kind of excitement, and 

 no longer close as before. They thus remain as if torpid for 

 some time, and generally do not recover their primitive sen- 

 sitiveness till after some hours. If, however, when they are 

 in this state of apparent torpidity, they are subjected again 

 to the action of the chloroform, they close as they did the first 

 time. It is not till after they have been chloroformed several 

 times, that they lose all kind of sensitiveness, at least until 

 the next day ; sometimes they even fade completely at the 

 end of too frequent repetitions of the experiment. In all cases, 

 the effects observed are the more marked in proportion to 

 the purity of the chloroform employed, and the degree of sen- 

 sitiveness in the plant. 



An analogous phenomenon is produced, if, instead of plac- 

 ing the drop of chloroform on the base of the petiole, it is laid 

 on the folioles situated at the extremity of a branch. The 

 folioles of this branch immediately begin to close pair by pair, 

 the common petiole droops, lastly, the folioles of the other 

 branches close in turn at the end of two or three minutes, the 

 nearest opposite leaf, and, if the plant be vigorous, most of the 

 other leaves situate below on the same stalk, follow their 

 example. When, after some time, the leaves open again, the 

 same want of sensitiveness is manifested as in the preceding 

 case. 



A singular feature in this phenomenon is the manner in 

 which the action of the chloroform is propagated from one 

 branch to another, then from one leaf to another, even when 

 the liquid disappears by evaporation almost as soon as it is 

 deposited. This action, as we have just seen, appears to be 

 communicated from the leaf to the stalk, following in the lat- 

 ter a descending direction ; generally the leaves situated be- 

 neath the chloroformed leaf are not at all affected. De Can- 

 dolle, in making an analogous experiment on a sensitive plant 

 with a drop of nitric or sulphuric acid, remarked, on the con- 

 trary, that it was the leaves above the leaf touched which 

 closed, without those situated beneath participating in this 

 motion.* The observation of our learned countryman is quite 



* l>e CandoUe Physiologie Vegetale, vol. ii., p. 8GG. 



